I think the same is true for any of the mainlines, including the Baptists....most if not 75% are apostate now
Mainlines over the years became about liberal secular culture. Parishioners abandoned them for non-denominational protestant churches or the conservative remnant within the old mainline.
Outfits like Bethel, the New Apostolic Reformation, the Emerging Church, a few other new movements are something else entirely.